1. Field of the Invention
The present invention relates to an apparatus and method of processing a bitstream of an embedded codec, and more particularly, to a packet processing apparatus and method which can reduce deterioration of sound quality caused by different arrival times of a plurality of packets at a receiving end when an output bitstream of an embedded codec is divided into the packets and transmitted accordingly.
2. Description of the Related Art
As services and network bandwidths become various, embedded codecs have actively been studied. Embedded codecs can provide voice and audio services of various qualities by supporting various bit rates using bitstreams which are formed in an embedded manner. The embedded codecs can process all of narrowband (300-3400 Hz), broadband (50-7000 Hz) and audio band (20-20000 Hz) signals. In other words, since a bitstream is formed in an embedded manner, the bandwidth and quality of a reproduced signal can vary according to how much of an encoded bitstream is extracted and decoded.
Generally, conventional voice codecs provide fixed bandwidths and bit rates. Therefore, the conventional voice codecs may be classified into narrowband codecs and broadband codecs according to bandwidths of signals processed. Adaptive MultiRate-Narrowband (AMR-NB) and Adaptive MultiRate-WideBand, which have been adopted as standards of the Third Generation Partnership Project (3GPP), provide various source qualities using diverse bit rates. However, according to these standards, a bitstream is not formed in an embedded manner. Instead, an independent bitstream is formed for each bit rate. Hence, if a bit rate changes, the operation of an encoder has to be changed. In other words, it is like having an independent encoder and decoder for each bit rate.
Q9 and Q10 of work package (WP) 3/study group (SG) 16 of the International Telecommunications Union-Telecommunication Standardization Sector (ITU-T) are currently standardizing embedded codecs. Specifically, Q10 is standardizing an embedded broadband codec which provides bitstream-level interoperability with G.729, which is a conventional narrowcodec widely used in an Internet phone (VoIP) service. In addition, Q9 is standardizing an embedded codec whose packet loss compensation rather than interoperability with a conventional codec is excellent.